September 13, 2013
Astronomers Reconstruct 3D View Of Our Milky Way’s Core
John P. Millis, PhD for redOrbit.com - Your Universe Online
Because of our location within the Milky Way, it is quite a challenge to get a bird’s eye view of our galaxy. To really get a sense for what our corner of the cosmos really looks like, astronomers have to take detailed measurements of billions of stars and attempt to accurately measure their distance from Earth.
Researchers at the Max Planck Institute for Extraterrestrial Physics (MPE) have now created the most detailed model of the inner structure of the Milky Way ever. Using publicly available data from the VVV survey, the team was able to reconstruct the peanut shaped bulge with an elongated bar that emanates from the prominent X-structure at the center.
Since our Sun is some 27,000 light-years from the region of interest - further complicated and obscured by regions of dense gas and dust - making accurate distance measurements has always proven a challenge. By exploiting features of red clump giant stars, the team was able to refine the distance measurements.
“While several studies with red clump giants and other methods have found evidence for a tri-axial structure of the galactic bulge, the depth of this star catalogue exceeds previous work and we can detect the entire population of red clump giants in all but the most highly obscured regions,” explained MPE's Christopher Wegg in a statement.
“From this star distribution we can then directly infer the three-dimensional density map, without the need to compare to theoretical models.”
Red clump stars are useful for this type of study because their surface brightness is, for all practical purposes, independent of their age or their particular composition. So by measuring their apparent brightness – the amount of light from the star as detected here on Earth – an accurate estimation of the distance to the object can be ascertained.
The only remaining problem is the galactic material that could be obscuring the object, making it appear dimmer than it is in actuality. But by studying the relative color makeup of the star, the effects of the intervening material can be accounted for.
“In our analysis we find that the inner region of our galaxy is in the shape of a box/peanut, with a highly elongated bar and a prominent X-structure,” says Ortwin Gerhard, who leads the dynamics group at MPE. “It is the first time that we can see this clearly in our own Milky Way, and the simulations in our group show that this shape is fairly characteristic of a barred spiral galaxy."